What was left out makes me wonder how PJ can manage to pull ROTK in under four hours...The book version of TTT had the Rohan/Fellowship going to Isengard to encounter the young hobbits and Sauruman, and the battle of Sam and Shelob, and Gandalf taking Pippin to Minas Tirith to meet Denethor. Those events will have to be incorporated into the final episode, which will really crowd things.
Don't forget, RoTK is not a very long story by itself. If you look at the book, fully one third of it is the Appendices. That's not to say that PJ won't cram lots of stuff into the movies; it can't be too long for me. I think the move to RoTK of the visit to Isengard and Frodo and Sam in Shelob's lair makes more sense. Everything will be resolved in the final movie. I'll enjoy the movie as it is and await the extended version of the DVD!